DNA, chromosome – DNA is found in the nucleus of the cell. DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.DNA consists of two long chains of nucleotides twisted into a double helix and joined by bases. A nucleotide is made up of sugar phosphate and bases. The four bases are: adenine and thymine or cytosine and guanine. DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule.

When a cell divides, both daughter cells need to have identical DNA to function properly. In order to get two identical sets of DNA the parent cell makes an extra copy before splitting. This process is called DNA replication. All cells must replicate their DNA prior to cell division. This assures that each new cell produced receives all of the genetic material necessary to survive (growth and repair) and reproduce.

Mitosis – to make body cells (all cells in the body except sex cells). This is to ensure that the chromosomes in the new cells after cell division have diploid number of chromosomes (same number as the number of chromosome in the original cell before division). For example body cells in all human have 46 chromomsomes.

Meiosis – to make sex cells (only in the gonads or sexual reproductive organs means in the ovaries for female and testes for males). This is to ensure that chromosomes in the new cells after cell division have haploid number (half the number of chromosomes in the original cell). For example sex cells (male gametes also known as sperm and female gametes also known as eggs) in human have only 23 chromosomes.

Chromosomes: – Chromosomes consist of DNA (double helix shape). Chromosomes contain genetic instructions of the living organisms and pass the characteristics of the organisms to the offspring (next generation). Chromosomes are found in the nucleus of the nucleus of plant or animal cell. Chromosomes are tightly packed so they fit into the nucleus of the cell.

Why is DNA replication important for cells?

When a cell divides, both daughter cells need to have identical DNA to function properly. In order to get two identical sets of DNA the parent cell makes an extra copy before splitting. This process is called DNA replication. All cells must replicate their DNA prior to cell division. This assures that each new cell produced receives all of the genetic material necessary to survive (growth and repair) and reproduce.

Cell division is the process that cells go through in order to divide and it is important for growth, repair (replacement) and reproduction. There are two types of cell division: meiosis and mitosis. Meiosis is the cell division to make new sex cells in the sexual reproduction. It takes place in the reproduction organs (in the ovary for the female and testis for the male). The other type, the cell division associated with growth and cell replacement or repair, is called mitosis.

Mutation is a change in the DNA sequence of a gene. It can be caused by radiation (UV, X-rays and harmful radiations from radioactive materials), food additives such a food colouring and chemicals such as agent orange (a defoliant used in the Vietnam war).

Chromosomes: – Chromosomes consist of DNA (double helix shape). Chromosomes contain genetic instructions of the living organisms and pass the characteristics of the organisms to the offspring (next generation). Chromosomes are found in the nucleus of the nucleus of plant or animal cell. Chromosomes are tightly packed so they fit into the nucleus of the cell.

Structure of DNA (Deoxyribonucleus acid)

DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.DNA consists of two long chains of nucleotides twisted into a double helix and joined by bases. A nucleotide is made up of sugar phosphate and bases. The four bases are: adenine and thymine or cytosine and guanine. DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule.Why is DNA replication important for cells?

When a cell divides, both daughter cells need to have identical DNA to function properly. In order to get two identical sets of DNA the parent cell makes an extra copy before splitting. This process is called DNA replication. All cells must replicate their DNA prior to cell division. This assures that each new cell produced receives all of the genetic material necessary to survive (growth and repair) and reproduce.

DNA -structure discoverd by Watson and Crick

6 Vocabulary

6.1 Bases: adenine and thymine or cytosine and guanine. Adenine is represented by “A”, Thymine by “T”, Cytosine by “C”, guanine by “G”. “A” links with “ T” while “ C ” links with “G”.

6.2 Cancer: is an uncontrollable cell division where it fail to produce differentiated cells.

6.3 Cell division: cell divides by pinching one cell into two.

6.4 Chromosomes: It contains genetic instructions of the living organisms and pass the characteristics of the organisms to the offspring.

6.5 DNA : DeoxyriboNucleic Acid (double helix structure -like a twisted ladder) DNA packed together to form chromosome so it can fit into the nucleus. A DNA Nucleotide: It is made made up of sugar, phosphate and base

6.6 Mitosis : a type of cell division to produce body cells with diploid number (same number of chromosome). This type of cell division produces cells for growth and repair.

6.7 Meiosis: a type cell division to produce sex cells with haploid number (number of chromosome is halved). This type of cell divison produces sex cells.

6.8 Mutation: is a change in the DNA sequence of a gene to some new, heritable form.

6.9 Replication: a process where a cell divides, both daughter cells need to have identical DNA to function properly. In order to get two identical sets of DNA the parent cell makes an extra copy before splitting in cell division.

Fossils Evidence (Fossil records may have missing pieces but they show life is old).

Radiometric dating (Carbon-14 dating is most useful for relatively recent fossils – up to 50 000 years old. Isotopes of other elements, such as potassium-40 are used to date rocks which are hundreds of millions of years old and so infer the age of fossils embedded in them. Other elements also have isotopes that are useful in fossil dating.)